1. Field of the Invention
The present invention relates to a device for measuring ambient light or flash light.
2. Description of the Prior Art
There has heretofore been disclosed a light measuring device equipped with a memory for storing two light measurement values in Japanese Patent Laid-Open No. 20323/1978. This light measuring device is constituted so that one light measurement value is obtained by a single measuring operation, and the thus obtained values are stored in the memory in due order. In addition, after the storage has been completed, it is feasible to specify desired light measurement values that are already stored therein. Exposure-calculation is performed on the basis of the specified light measurement values and the calculated result is arranged to be displayed.
A light measuring device disclosed in Japanese Patent Laid-Open No. 77725/1981 subsumes: a memory for storing a plurality of light measurement values; a first display means for lighting up one of the display elements arranged in a predetermined direction in accordance with a stored light measurement value; and a second display means for displaying numerals on the basis of a stored light measurement value. The second display device displays the numerals corresponding to the specified light measurement value among a multiplicity of light measurement values stored in the memory.
In either device, the number of light measurement values allowable to be stored in the memory is determined beforehand and storage capacity is therefore confined. In the above-described conventional devices, the user is unable to ascertain the number of the light measurement values which are now stored in the memory and hence it is impossible to confirm the residual capacity of storage.
In the aforementioned light measuring device disclosed in Japanese Patent Laid-Open No. 77725/1981, a display element corresponding to the stored light measurement value is indicated by the first display means. However, if a plurality of the already stored light measurement values are the same, a plurality of the light measurement values will correspond to one display element, whereby it is unfeasible to ascertain the number of the light measurement values stored in the memory.
There is broadly known a flash light measuring device having a switch turned ON in order to set the device to a condition for measuring a flash light. This kind of device is constituted such that, the switch is turned ON, and after enabling the light measuring device to measure the flash light by turning ON of the switch, the measurement is started by receiving the flash light. In such a constitution, however, at the moment of completing one measurement of light, the reception of the flash light is inhibited. As a result, when measuring the flash light once more, the switch is turned ON again and the flash light must be set in a receivable state. Furthermore, this arrangement virtually requires an operator who manipulates the light measuring device and another operator who manipulates a flash light source.
In regard to a device for measuring a quantity of flash light, a well-known type is the one which is capable of selecting either a single measurement mode or a continuous measurement mode, the former measuring an amount of the light emitted once by a flash device to display it, the latter successively integrating amounts of the light consecutively emitted by the flash device. According to this device, a light measuring circuit, provided for producing an electric signal corresponding to the amount of light received, is set to an operable condition by operation of a predetermined key. Here, the integrated amount in the continuous measurement mode is reset by the operation for permitting a new integration. However, it is impossible to reset the integrated amount in the continuous measurement mode by the operation of the predetermined key in the single measurement mode in which the light measurement is started by the operation.
Additionally, in a flash photographing mode in which an object is photographed by illuminating it by light emitted from a flash device, there is a case in which a shutter speed is determined to a flash synchronization speed while an aperture value is determined in accordance with a depth of field and so on. In such case, the following conventional method is adopted in order to obtain a proper exposure with respect to the object to be photographed. Namely, a proper distance from the flash device to the object should be found out with using the combination of the determined shutter speed and the determined aperture value, with repeating the measurement while varying the distance. However, this conventional method needs a great deal of time until a proper exposure condition is achieved and complicated operations must be repeated.
Furthermore, in a photographic exposure meter, a proper combination of a shutter speed and an exposure value for obtaining a proper exposure is displayed in accordance with the brightness of an object to be photographed or with the luminance thereof. For example, a combination of a preset shutter speed value and a proper aperture value calculated for obtaining a proper exposure is displayed in a shutter speed priority mode, while a combination of a preset aperture value and a proper shutter speed calculated for obtaining a proper exposure is displayed in an aperture priority mode.
However, in such a photographic exposure meter, only a combination of a shutter speed and an exposure value is displayed after a conpletion of light measurement. Therefore, it is difficult to distinguish a preset value from a calculated value in the displayed combination. Additionally, if the newly measured result is the same as that of the previous result, it is not easy to recognize whether the new measurement is virtually effected or not.